topic 8 - tonicity and osmoregulation

osmosis

the diffusion of water from areas of low solute concentration to areas of high solute concentration

tonicity

the ability of an extracellular solution to cause a cell to gain or lose water. depends on the concnetration of solutes that cannot pass through the cell membrane

hypertonic

concentration of solutes is higher outside than inside the cell, causing it to llose water to the extracellular fluid and shrivel and die

isotonic

the concentration of solutes inside the cell is equal to the outside of the cell. there is no net movement of water

hypotonic

concentration of outside solutes is less than inside, causing the cell to gain water and swell

osmoregulation

cells must be able to regulate their solute concentrations and maintain water balance. animal cells react differently than plant cells

plasmolysis

in plant cells, the central vacuole shrinks due to hypertonic solutions and the plasma membrane pulls away from the cell wall

cytolysis

in animal cells, when placed in a hypotonic solution, the cell swells and expands eventually bursting and lysing, releasing its contents

turgid

a plant cell that is swollen and firm due to high internal water, or turgor pressure which pushes the cell membrane against the cel wall. Prevents plant cells from collapsing and plants from wilting

homeostasis

the process where organisms maintain a stable internal environment despite external changes